NZ226978A - Capsule with thermoplastic floor for conveying plugging agent to borehole drilling fluid sink - Google Patents

Description

# 22 6 9 7 8 f'.rjr.'y Qaj; Ur.^cr ihe provisions of Regu- S;.:-"--~ucn r.:s been sr.to-da'cd > ' " '.z^ • * V- * 1Q r'- ,w,'»**•* •• ^c... 1/..! Initials Patents Form No. 5 ,. :x- !■']>/ ■ 2'i ••/ r<- KEV; ZEALAND 29J JAN 1990 /- •<. 1 6 NOV 1988 ^ V,-v. *<*, X/ e P , Vj PATENTS ACT 195 3 COMPLETE SPECIFICATION METHOD AND DEVICE FOP CONVEYING CHEMICALS THROUGH 30REH0LE x/We, TAKENAKA KOMUTEN CO., LTD., of 27 Konr.achi 4, Kigashi-ku, Osaka-shi, JAPAN; and SEKISO CO., LTD., of Komor.cocho 4-22, Kakata-ku, ^ukuoka-shi, JAPAN; companies duly orqanized and existing under the laws of JAPAN, hereby declare the invention, for which xyvre pray that a patent ray be crantec to xxx'us, and the r.ethod by v:hich it is to be Derfor~-~ l>'~ v- t <► o be pc.rticclariy described in and by the following statement: (FOLLOWED BY PAGE la) r- o r> o •** METHOD AND DEVICE FOR CONVEYING CHZXICALS THROUGH BOREHOLE FIELD OP THE INVENTION The present invention relates to means for transporting a certain amount of plugging chenicals through a borehole to a desired depth such that the plugging chemicals are not mixed with drilling r.uc.

BACKGROUND OF THE INVENTION Trial pits are formed for purposes of exploration for petroleum, geothermal energy, minerals, etc. Since these pits are as ceep as 500 to 5000 m, lost circulation, or lost returns, .-nay take place during a boring operation. If this phenomenon occurs, the drilling mud escapes into the earth through porous sicewalls, making it impossible to retain the head of the drilling muc. This may bring the porous sicewalls to destruction.

In order to plug up the gap that causes such lost circulation, plugging chenicals are supplied to the location of the lost circulation. Originally, a supply pipe was inserted into the ground to supply the chemicals. Specifically, the chemicals are conveyed through the pipe in such a way that drilling mud is followed by the chemicals, thus forming so-called mixed-phase fluid. 22 6 9 78 However, chemicals for stopping lost circulation differ from drilling mud in specific gravity, viscosity, surface tension, and other characteristics. Therefore, when chenicals which are not diffused are employed, they move downward through drilling mud. During this process, the chemicals are not mixed with the drilling mud, nor is a mass of fluid formed. Wrinkles are formed inside the pipe at the rear end. The chemicals move down the pipe while causing the wrinkles to vibrate. Therefore, a small mass is torn out of the mass of fluid at the position of one rear wrinkle. This small mass drifts within the pipe, increasing the area with which the chemicals come into contact with the drilling muc. This is undesirable for the chemicals that should be conveyed without being mixed with drilling mud. Thus, this supply is a wasteful method, and in which it is difficult to pump an almost complete mass of fluid through the pipe to the location of lost circulation.

In an attempt to avoid this problem, i.e., to convey chemicals in the form of a mass to a desired place without reducing the amount of the chemicals, capsules charged with chemicals have been used. These capsules permit chemicals to be transported without being mixed with drilling mud. One method heretofore proposed to 22 6 8 7 8 diffuse chemicals our of the capsule that has reached the bottom of a hole is to destroy the whole capsule.

Another proposed method is to open the valve mounted at the front end of the capsule.

When the former methcc is adopted, a destruct mechanism such as an explosive that is required to be carefully handled is needed. Further, porous sicewalls may be destroyed, depending on the cestruct mechanism. In addition, the incorporation of the destruct mechanism into a capsule renders the structure complex and reduces the amount of chemicals contained in the capsule accordingly. '•■hen the latter method is utilized, it is not assured that the valve at the front end of the capsule is opened with certainty, because of the water pressure inside the hole, the natures of the drilling mud and slime, and other factors.

SUMMARY OF THE INVENTION It is an object of the present invention to '>«.✓ provide a method of conveying chemicals to a desired depth within a borehole such that the porous sicewalls of the hole are net destroyed, or at least to provide the public with a useful choice.

It is another object of the invention to provide a capsule adapted for the conveyance of chemicals as described in the previous paragraph. • ~ According to the present invention there is provided a method of conveying plugging chenicals down a borehole, comprising the steps of: providing a capsule either totally mace of a thermoplastic material or having a bottom plate formed of a thermoplastic material; and filling the capsule with plugging chemicals for stopping loss of drilling fluid circulation in the borehole; and lowering the capsule toward a location of loss of drilling fluid circulation so that the capsule or its bottom plate is softened by heat at an elevated temperature rone, thereby releasing the plugging chemicals from said capsule.

According to the present invention there is further provided a caPsule suitable for conveying plugging chemicals down a borehole, comprising a capsule either totally made of a thermoplastic material or having an end closure made from a thermoplastic material, wherein the -thermoplastic material is adapted to soften at an elevated teaperature to enable the release of plugging chemicals.

Other objects and features of the invention will appear in the course of the description thereof which follows.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a capsule that is totally made from a thermoplastic resin in accordance with the invention; Fig. 2A is a front elevation of another capsule jp 18 SEP 1989 £; # 22 6 9 7 g 4^ according to the invention, the capsule having a bottom plate mace from a thermoplastic resin; Fig. 23 is an exploded perspective view of the capsule shown in Fic. 2A; Fig. 3 is a diagram for illustrating the temperature distribution through a drilled hole; Figs. 4 A and 43 are views for showing the manner in which the capsule shown "in Fig. 1 is used; Figs. 5.-.-5C are views for showing the manner in which the capsule shown in Figs. 2A and 23 is used; Fic. 6 is a sersoective view of a further caDsule Fig. 7 is a diagram for illustrating the temperature distribution through a drilled hole; Fig. 6 is a perspective view of a weight that is usee with the capsule shown in Fig. 6; Fics. 5A-2D are views for showing the manner in which the capsule shown in Fig. 6 anc the weight shown in Fic. S are used; Fig. 10 is a perspective view of a still other capsule.

Fig. 11 is a perspective view of the bottom plate of the capsule shown in Fig. 10; Fig. 12 is a view for illustrating the manner 22 6 9 7 8 in which the hotter, plate shown in Fig. 11 is destroyed; Fics. 13A-13D are views for showing the manner in which the capsule shown in Fig. 10 is used.

DETAILED DESCRIPTION OF THE INVENTION deferring ro Fig. 1, there is shown a capsule embodying the concept of the present invention. This capsule,indicated by reference numeral 1, is designed simply ro hold chemicals, and is totally mace from vinyl chloride resin, vinyl acetate resin, acrylic resin, polystyrene resin, polyethylene, cellulosic plastic, or other thermoplastic resin that softens when heated.

The material and the thickness of the capsule 1 are selected by taking account of the temperature at the depth in a drilled hole where lost circulation occurs, the time taken for the capsule to reach the depth, the time taken for the capsule to soften or melt, and other factors. Approximate temperatures at which thermoplastic resins soften or melt are as follows. soft vinyl resin 40 to S0°C hard vinyl resin 60 to 80°C vinyl acetate resin 50 to 100°C acrylic resin 80 to 150°C The time taken for these resins to soften or melt ranges from about 10 to 30 minutes. The temperature distribution through a drilled hole 2 is shewn in Fig. 3. The top cover of the capsule 1 shown in Fig. 1 has an opening la through which chemicals are introduced. Also, the capsule 1 has retaining portions lb to which a wire 3 is anchored. Preferably, the capsule tapers forwarciy as shown, because of the reasons described belcw. First, boreholes such as the hole 2 are relatively rarely vertical. Some boreholes are inclined at 30° or 45°. Secondly, the porous sicewalls are not fiat but rough. Accordingly, in order to allow the capsule to crop smoothly, the capsule must have a self-guidinc function. capsule according to the invention is shown. The body 4 of the capsule acts simply as a container and takes the form of a cylinder. The body 4 is mace of a steel tube or made from a heat-resistant, glass fiber-reinforcec plastic (FR?) or the like. The top cover of the body 4 has an opening 4a through which chemicals are introduced. A wire 3 is anchored to retaining portions 4b. The body 4 is designed to be recoverable. An end closure 5 is fitted over the body 4. In the illustrated example, the end closure 5 has a tapped portion 5a that is screwed to a threaded portion 4c formed on the body 4. Th Referring next to Figs. 2A and 23, another 7 0&*.

O o is made from the same material as the af ore.-er.tionec capsule 1. Thus, the end closure 5 softens or melts at high temperatures, and can be detached from the body 4.

As can be understood from the description thus far made, the capsule mace from a thermoplastic resin is caused to soften or melt to diffuse the chemicals contained in it in the manner described belcw. The capsule 1 shown in Fig. 1 is cropped to a location where lost circulation takes place, as shown in Fig. 4A. Then, the capsule 1 is softened or aelts at the elevated temperature, allowing the chemicals to be released. This seals up crevices 6. Subsequently, the wire 3 is pulled up, as shown in Fig. 4B.

The capsule shown in Figs. 2A and 23 is caused to fall to the location of lost circulation, as shown in Fig. 5A. The end closure 5 then softens or melts, so that the chemicals may be released. As a result, crevices 6 are sealed up, as shown in Fig. 53- Thereafter, the body 4 of the capsule is pulled up, as shown in Fig. 5C.

The novel capsules designed as mentioned above yield the following advantages. (1) It is possible to certainly diffuse the 226 9 7 8 (2) The capsules seal up the fissures when V softened or molten. (3) No mechanism is needed to destroy the capsules. (4) Since the capsules are simple in structure, it is easy to carry out the work. (5) Stoppage of water can be effected at any cesirec location including intermediate positions on porous sicewalls. (6) The capsules are economical to fabricate -Especially, the bocy of the capsule having the meltable bottom plate can be repeatedly used. Further, the capsule is quite cheap, because the bottom plate is cheap. (7) Where the capsule that is totally meltable " is used, after one capsule is cropped, another can be caused to move cown. In this way, the work can be executed efficiently. Especially, when a large-scale lost circulation takes place, the capsule can be used to advantage. deferring to Fig. 6, there is shown anotner form of capsule. Tne capsule, indicated by numeral 101, is cnarged - with ch-emicals for stopping lost circulation, and is mounted on a drilling rod in such a manner that it embraces the rod -The capsule 101 is annular in shape and centrally provided with a hole in which the rod is loosely mounted. In the illustrated example, the capsule is molded entirely out of a material, and is attached to the rod at its one er.c. Where it is desired to mount the capsule on the rod at an intermediate location, the capsule is vertically divided into two sections which are joined together with a pin. drilling rod through the hole until it strikes on a rig. The capsule 101 is made from a resin such as glass fiber-reinforcec plastic. Magnets 102 are embedded in the capsule around the fringe at the upper end. The magnets 102 are used to attract a messenger member (described later) for recovering the capsule. The capsule has a end closure 2Q3 -which preferably tapers off to reduce the resistance encountered when it falls. The end closure 103 is made from either a fragile material such as glass or a material that melts when heated, such as vinyl chloride resin, vinyl acetate resin, acrylic resin, polystyrene resin, polyethylene, cellulosic plastic, or other thermoplastic The capsule 101 is guided smoothly along the resin that softens when heated cv* 1 3 SEP 1989 n>'!} "G°.

^ A/ C r" o The material anc the thickness of the end closure 103 are selected by taking account of the temperature at the depth in a drilled hole where lost circulation occurs, the time taken for the capsule to reach the depth, the time taken for the capsule to soften or melt, ar.d other factors. Approximate temperatures at which thermoplastic resins soften or melt are as follows. soft vinyl resin 40 to £0°C hard vinyl resin 60 to 60 °C vinyl acetate resin 50 to 100°C acrylic resir. SO to 150°C The time taken for these resins to soften or melt ranges from about 10 to 30 minutes. The temperature distribution through a drilled hole is shown in Fig. 7. When the capsule 101 is to be used, chemicals are injected into it ur.cer the condition that the end closure 103 is not yet mounted to the body of the capsule- After the completion of the injection, the bottom plate is mounted to the body to close the capsule. It is also possible to form an opening in the top cover of the capsule for introduction of chemicals. deferring next to Fig. 8, there is shown a weight 104 that is used to withdraw the capsule 101 shown in Fig. 6. The weight 104 is shaped into an annulajr^f: c. N / /' to permit it to be cuiced along a drilling rod when it falls through a drilled hole, in the same manner as the capsule 101. Again, the weight nay be split into plural sections in the sane manner as the capsule 101. are disposed on the weight 104 to attract the capsule 101. The weight 106 is suspended by a wire 106. The weight 105 is caused to move ccwn a drilled hole such that it follows the capsule 101. Then, the end closure 103 that is not vet: broken collides with a rig with certainty and breaks. The vacant capsule 101 is attracted, pulled up, and recovered for reuse. the capsule 101 is now described by referring to Figs. 9A-9D. First, the capsule 101 is mounted to a drilling rod 10S, and ther. the rod is lowered, as shown in Fic. 9A. The capsule 101 collides with a rig I03a and conies to a halt. At this tine, if the end closure 103 is mace from a fragile material, then it may break. If it is made from a material that melts when heated, then it melts with time, diffusing the chemicals. Subsequently, the weight 105 is moved down the hole, as shown in Fig. 93. The weight 105 then collides with the capsule 101 from behind. This certainly destroys the enc* closure 103 made from a ■iagnets 105 correspor c to the magnets 102 e manner in which chemicals are conveyed with 12 22 6 S 7 fragile material. Also, the weight 105 magnetically attracts the capsule 101, so that both are coupled together, as shown in Fic. 9C. Finally, the wire 106 is crawn upward to recover the capsule 101, as shown in Fic. SD.

The chemicals are allowed to spread while the drilling roc is not pulled away. Therefore, if the chemicals react with the slime at the bottom of the hole and solidify, then rotation of the rig may be hindered. In order to circumvent this undesirable situation, the rod is raised to a certain height before the capsule is lowered. The chemicals are enabled to spread at the certain height above the bottom. The chemicals crop as a mass to the location of lost circulation and solidify, but no problems take place in restarting the rig of the rod. The capsule constructed as mentioned thus far yields the following advantages. (1) Since it is not necessary to pull up or lower the drilling roc, the time required for the execution of work is short. (2) Since it is not necessary to pull up the drilling roc, it is possible to let down the capsule immediately after the occurrence of lost circulation, for stopping the flow of water. Consequently, only a small 226978 amount of drilling mud is necessitated to stabilize porous sicewalls. (3) Since the capsule is guided along th« drilling rod, the capsule can be certainly conveyed to a desired depth where lost circulation takes place. (4) Depending on the condition of lost circulation, several capsules may be let down to stop the flow of issuing water. (5) The capsule can be handled easily because of its shape and because the bottom plate is replaceable. (6) Since only the broken bottom plate is replaced with another, the cost is low.

Referring next to Fig. 10, there is shown another form of capsule. The capsule, indicated by numeral 201, contains chemicals for stopping lost circulation. This capsule 201 is annular in cross section and centrally provided with a hole 201a in which a drilling rod is loosely inserted. Thus, the capsule 201 is mounted on the rod so as to embrace the rod. In the illustrated example, the capsule is totally molded out of a material. The capsule is mounted on the rod at its one end. Where it is desired to mount the capsule at an intermediate position on the rod, the capsule may be divided vertically into two sections which are coupled ^ O «.• i r» c. n p . ■ ■ together with a pin. The capsule 201 is guiced along the rod and thus coves down the hole smoothly until it strikes on a rig. end closure 202, which is mace from a fragile material such as glass or ceramic. As shown in Fig. 11, vertically extending protrusions 202a are formed integrally with the end closure 202 and circurnferentiallv disposed on the top and bottom surfaces of the end closure 202. The upwardly extending protrusions 202a acz as legs that allow the end closure 202 to be fitted into the capsule 201 with certainty. As shown in Fig. 12, the downwardly extending protrusions 202a are forced between the neighboring knife edges of a rig 203a. As the rig 203a is rotated, the protrusions destroy the checkerboard-like plate. chemicals are introduced into the capsule 201. Then, the end closure 202 is mounted tc. close up the capsule. It is also possible to form an opening in the top cover of the capsule to permit chemicals to enter it. A wire 204 is used to suspend the capsule when the velocity of the descending capsule is controlled.

Chemicals are conveyed through a drilled hole 205 along a drilling rod 203 by the capsule 201 in the The capsule 201 is mace of paper except for its Before the end closure 202 is mounted *s £ SEP 5989 r £~' ^ «- -V O ^ • / C manner described below. the illustrated example, chemicals are diffused while the rod 203 is not withdrawn. Therefore, there arises the possibility that the chemicals react with slime at the bottom of the hole and solidify, hindering rotation of the rig 203a. This situation can be avoided in the manner described below. 2 03 is brought to a stop. Then, the roc is upwardly moved a certain distance of 10 to 20 m, as shown in Fig. 13A. The capsule 201 is mounted on the rod 203 and let down until it collides with the rig 203a and comes to a halt, as shown in Fig. 133. The rod 203 is then rotated, causing the rig 203a to destroy the end closure 202.

Thus, the chemicals are diffused. Subsequently, the rig 203a is turned slowly to prevent adhesion of the diffused chemicals and to break the swollen capsule 201, as shewn in Fig. 13C. The chemicals are scattered at a certain level above the hole bottom, crop toward the location of lost circulation as a mass, and solidify. However, no problems arise in restarting the rig of the rod. The pieces of the broken plate are sucked into the place of lost circulation. As a result, the sucking hole is plugged up. After checking the stoppage of the flow of When lost circulation occurs, the drilling rod water, the drilling work is restarted 16 The capsule constructed as described above yields the following advantages. (1) Since it is not necessary to pull up or lower the drilling rod, the'time required for the execution of work is short. ' (2) Since it is not necessary to pull up the drilling roc, it is possible to let down the capsule immediately after the occurrence of lost circulation, for stopping the flow of water. Consequently, only a snail amount of drilling mud is necessitated to stabilize porous sicewalls. (3) Since the capsule is guided along the drilling rod, the capsule can be certainly conveyed to a desired depth where lost circulation takes place. (4) Depending on the condition of lost —- circulation, several capsules may be let down to stop the flow of issuing water. (5) Since the capsule 1 is a throwaway capsule, specialist's help is not needed. Hence, the capsule can be .* . handled easilv. (6) Since the body of the capsule made of a paper tube breaks into pieces, the capsule is effective in filling up fissures. £"? r o -o W <_ / ^

Claims (15)

WHAT WE CLAIM IS:

1- A method of conveying plugging chemicals down a borehole, comprising the steps of: providing a capsule either totally made of a thermoplastic material or having a bottom plate formed of a thermoplastic material; and filling the capsule with plugging chemicals for stopping loss of drilling fluid circulation in the borehole; and lowering the capsule toward a location of loss of drilling fluid circulation so that the capsule or its bottom plate is softened by heat at an elevated temperature zone, thereby releasing the plugging chemicals from said capsule.

2. A method as claimed in Cleim 1 wherein said capsule is raised and lowered into said borehole by means of a wire attached thereto.

3. A method as claimed in Claim 1 wherein said capsule surrounds a drilling rod and can be delivered to the site of loss of drilling fluid circulation by lowering said capsule along said drilling rod.

4. A method as claimed in Claim 3 wherein the upper end of said capsule is provided with magnets and^i <°\\ ov\ - 18 - - ^8 SEP 1989 4 /-I Q.£r/ 7"S capsule is recovered by lowering a magnetised weight down said drilling rod until it attracts said capsule and then raising the magnetically coupled weight and capsule.

5 A capsule suitable for conveying plugging chemicals down a borehole/ comprising a capsule which is adapted to surround a drilling rod and slide therealong, said capsule being either totally made of a thermoplastic material or having an end closure mace from a thermoplastic material, wherein the thermoplastic material is adapted to soften at an elevated temperature to enable the release of plugging chemicals.

6. A capsule for conveying chemicals down a borehole as claimed in Claim 5 comprising: a capsule body made of steel or made from a heat-resistant, glass fiber-reinforced plastic; and an end closure fitted into or over the capsule body, the end closure being made from a thermoplastic resin that softens and permits chemicals contained in the capsule to be released when the capsule reaches a certain t erapera t ure .

7. A capsule as claimed in Claim 5 or 6 wherein the body of the capsule tapers towards the lower end thereof.

8. A capsule as claimed in any one of Claims 5 to 7 wherein the end closure is fitted over or into the body of the capsule.

9. A capsule as claimed in any one of Claims 5 to 8 0 0/ ^ t '? ^ ^ ^ ^ ' '

10. A capsule as claimed in Claim 5 wherein said capsule is divided longitudinally into two sections and is engageable with an intermediate portion of a drilling rod.

11. A capsule as claimed in any one of Claims 5 to 10 wherein magnets are provided at the upper end of said capsule.

12. A capsule as claimed in any one of claims 5 to ll wherein the capsule body is tubular.

13. a capsule as claimed in any one of the preceding claims wherein the thermoplastic material is vinyl chloride resin, vinyl acetate resin, acrylic resin, polystyrene resin, polyethylene or cellulosic plastic.

14. A method of conveying chemicals down a borehole as claimed in claim 1 substantially as herein described with reference to the accompanying drawings and in respect of any one of the embodiments of the invention.

15. A capsule for conveying chemicals down a borehole as claimed in claim 5 substantially as herein described. TAKELiAKA KOilUTErJ CO. LIMITED and SBKISO CO. LIMITED by their attorneys